In order to learn how environmental contaminants may affect health, researchers increasingly turn to biomonitoring of human blood, urine, breast milk, and other tissues, and to sampling in personal spaces, such as testing dust and air in homes. New tests measure low levels of a wide range of chemicals -- recently including phthalates, bisphenol A, brominated flame retardants (PBDEs), and perfluorinated compounds (PFOA), among many others. While the scientific aim is to analyze patterns in populations, study participants often want to learn their own individual results. The goal of this project is to develop guidelines for ethical practices in decisions about whether and how to report personal exposure results to participants when the health implications are unclear and the effectiveness of exposure reduction strategies is uncertain. As a basis for proposing ethical practices, this project investigates the experiences, values, and attitudes of participants in personal exposure assessment studies and the perspectives of IRB members, researchers, clinicians, and legal experts. Researchers and institutional review boards (IRBs) charged with protecting human research participants must respect the autonomy of study participants; weigh the benefits of reporting results, which may contribute to science literacy and inform and empower participants to take action; and consider the potential for harm, for example, from misplaced worry, stigma, or ineffective action. They also must consider legal or financial issues that may arise when contaminants are detected in a private place, such as a home. Because biomonitoring and personal exposure measurements have expanded rapidly, few models exist for reporting practices; and a 2006 National Academy of Sciences report identified a pressing need for empirical research into individual exposure report-back. This project helps to fill that gap. The specific aims are (1) to conduct four case studies of research that has reported individual results for chemicals for which health effects are uncertain, and for each study to (a) analyze informed consent and report-back methods and (b) conduct in-depth interviews with study participants, researchers, and IRB members; (2) to conduct legal research that examines how obligations to disclose hazards under federal and state real estate and environmental laws might be triggered by measurements in homes and how disclosure obligations might conflict with participants' privacy; (3) to conduct three focus groups to further examine multiple perspectives and stimulate dialogue among researchers, IRB officials, lawyers, clinicians, and community health advocates, and (4) based on results of the other specific aims, develop, peer review, and disseminate guidelines for effective, ethical, and logistically feasible report-back protocols for personal exposure research. The four case studies encompass government, academic, and advocacy research with adults and children, including the pilot study for California's Biomonitoring Program, a cohort health study, a biomonitoring study of PFOA exposure from drinking water, and advocacy biomonitoring studies of the need for better US chemical policies.